Dynamo-electric machine.



v. A'. FYNN.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED JUNE 17, 1911.

Patented July 21, 19M

3 SHEETS-SHBET 1.

IIVVENTOR WITNESSES:

Valre A. Fynn.

ORNEY V. A. PYNN.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED JUNB17,1911.

Patented July 21, 1914.

3 SHEBTSSHEET 2.

INI/ENTOH WITNESSES:

I I m Valere .A.Fynn WW4, ronwu V. A. PYNN. DYNAMO ELECTRIC MACHINE. APPLIGATION FILED JUNE 17, 1911.

1,104,184. Patented July 21, 1914.

3 SHBETSSHEET 3.

WITNESSE QC 7? 11 0.0L

of operation.

place it in a field structure in which can be 1 producedeithernor 3n electrical poles. Thus unrrnn sTATEs PATIENT OFFICE.

A ER E A FR D YNN, 0F I- Q EN LAND, (AS-$ 331. 3 O WAGNER E E I LOU S, M SSO R A R 03 N YNAMO-EL TR C MAQHINE- Specification of Le ter atent- Paten ed-July 21. 13914.

Application filed zTune 17, 1911. seniahll'oumflifi.

To all whom 't may concern Be it known that I, VALisRn Am nno F- em, a subject of the King of England, residing at London, England, have invented a certain new and useful'Dynamo-Electric Machine, of whichthe following is such a full, clear, and exact description as will enable any one skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, forming part of this specification.

My invention relates to dynamo electric machines and particularly to those required to run at widely varying speeds and to 1 charge storage batteries.

My objects are to produce a dynamo suit-- able for such service in which as little material as possible will be required at low speeds and which will have good commutating properties throughout its whole range In'all such dynamos it isnecessary to reduce the effective magnetization of the machine with increasing speed or with increasing current output. I accomplish this reduction by causing the effective-exciting E. M. F. to suitably change its magnitude and in some instances I supplement this reduction 1 of the effective exciting E. M. F. by means of a magneto motive force adapted to influen'ce the terminal voltage of the machine directly as well as indirectly. The direct influence of this M. M. F. on the terminal voltage is obtained by causing said M. M. F. to directly aflect the magnitude of the efl'ective magnetizationof the machine. Its indirect influence is obtained by affecting the effective magnetization of the machine in such a way as to thereby also affect the magnitude of the effective exciting E. M. F. l

In carrying my invention into practice I provide an armature wound for n poles and in one form of my improved dynamo I make I use in connection with an n pole armature of l afield structure provided with 3n mechanical poles. In all easel; I derive the exciting E. M. F. from the armature itselfand to this end I make use of main brushes and of at least one exciting brush displaced from the nearest main brush by l20/n degrees -connccti ng all the main exciting windings between one main and one exciting or auxiliary brush ordividing the ma'in exciting windings into two groups and connecting each between a main and an auxiliary brush. 'llhis displacement of the brushes in connection with the field structure having 3n mechanlcal poles allows-each of said brushes to be placed H1 an intcrpolar space. At low speeds I prefer to magnetize adjacent sets of 'three mechanical poles in opposite directions thus obtaining the equivalent of an le -pole field structure and utilizing the available material to the best advantage. high speed I refer to magnetize adjacent mechanical poles in opposite directions thus obtaining a true 3n. pole field structure. While a 3n pole field is not economical in connection with an n-pole armature yet it should be remembered that the effective magnetic flux required at high speeds is of course very much smaller than at the low speeds and a true 311. pole field can therefore be used without necessitating an increase in the size of the machine. The

advantage of a true 31?. pole field is that each brush can then be placed not only in an nter-polar space but in a true peutral zone thus greatly improving the commutation conditions. The greatest commutating difficuities arise at the higher speeds and it is for this reason that I prefer to work with a 3n pole field at those higher speeds. At the lower speeds the commutation does not present any serious difliculties and I prefer to work with an n-pole field thus making the fullest use of the active material at a time when I require the greatset amount of such material. In order to change the polarity of thefield from n to 3n poles I prefer to make use of a M. M. F, which afl'ects the terminal voltage of the machine directly as well as indirectly.

My invention will be better understood by reference to the accompanying diagram ma-tic drawings in -which' Figure "1 shows a simple form of my involition; Fig. -2 indicates an arrangement by which the active material is more fully utilized than in Fig. 1; Fig. 3 shows the preferred form of the dynamo and Fig. 4 shows composed of three independent magnets 36,

31', 38, each having two poles and each of these poles embracing rather less than onesivth oi the circumference of the armature or rotor. The poles N 8 and N S of the nuwnets 36 and 37 embrace adjacent sections of the armature while the poles N S of nugnet embrace armature sections which are located midway between the sections em- :ced by the poles or" the magnets 36 and The main brushes 5 and 6 are so located to short circuit coils lying between the aduccnt poles of the magnets 36 and 37, while the auxiliary brushes 7, 8 are displaced from the main brushes 5, 6 by 60 electrical de grees. lirush 7 is located between a pole of the magnet 37 and a pole of the magnet 38; while brush 8 is located between a pole of the magnet 36 and a pole of the magnet 38. Each of the poles carry exciting coils. The main exciting coils 9, 10, 11, 12 are located on the poles of the magnets 36 and 37 and are connected in series between the main and the auxiliary brushes. This exciting circuit can be traced as follows: From the main brush 5, through the exciting coil J on the pole S to the coil 10 on the pole N. to brush 7. through the commuted winding 3 to brush 8, through coil 1:2 on the pole S to coil 11 on the pole N to the main brush 6, and back to the main brush 5 by way of the commuted winding 4. The reversing coil 13 located on the pole S is connected between the main brush 6 and the terminal 2 of the dynamo. while the reversing coil 14 is connected between the main brush 5 and the terminal 1. The translating device to be operated by this dynamo is of course, to be ('ODHQCtCd to the terminals 1 and 2. The op eration of this simplest form of my invention is somewhat as follows:

Assuming the connections to be such as shown and the machine to be running on open circuit and in a counterclockwise direction then the remnant magnetization will cause an exciting current to flow through the cs-ils 9. 10, 11, 12 assumed in the figure to lion in the direction indicated by the arrows,--that is, from the brush 5 to the brush (3, thus magnetizing the poles of the magnets 36 and 37 as indicated by the capital letters designating their polarity. N0 (tn-rent will flow through coils 13 and 14 as long as there is no load on the machine and the poles N and S will therefore be nontral except for such remnant magnetism as may be present in said poles. The conditions will be identical with those obtained in an ordinary two-pole dynamo with the exception that each of the magnetic poles is here split into two mechanical ones, thus the north pole is composed of the pole N belonging to the magnet 36 and N belonging to magnet 37, while the south pole is similariy divided. Only part of the armature conductors will be active under these conditions. These conductors are indicated by dots and crosses placed inside the circles illustrating the two armature windings. It is seen that all the E. M. F.s generated in the winding 4 are added at the brushes 5 and 6, while all the E. M. Ffs generated at the winding S cancel each other with respect to the brushes 7, 8 and the voltage appearing at said brushes is therefore zero. At noload and at any speed the excitation of the machine is therefore only dependent on the E. M. F. generated at the brushes 5, 6. Since the poles S and N are neutral then the corresponding armature segments are idle and the material of the machine is not utilized to the best advantage. It is to be observed that the armature reaction due to any current circulating in the winding 4 and directed by the brushes 5, 6 cannot set up any appreciable flux because of the lack of all magnetic connection between the magnets 36 and 37. The current circulating in the winding 3 by way of the brushes 7, 8 is comparatively small but part of the ampere turns due to it can produce a flux through 36 or 37. Any such flux may as a rule be safely neglected.

As soon as the dynamo is loaded then the load current circulates through the reversing coils 13. 14 and magnetizes the poles of the magnet 38 proportionally to the load. In F ig. 1 these reversing coils are so connccted as to magnetize said poles in a manner to secure a true 6 pole field, as indicated by the capital letters, thus affecting the magnitude of the efi'ective magnetization of the machine. The M. M. F. set up by the coils 13, 14 is responsible for an E. M. F.

in the. commuted winding 4. the direction of which is indicated by a single dot and a single cross placed on the center line of the poles N S and it is seen that this E. M. F. opposes that generated in the other sections of that winding. In this way the M. M. F. produced by the coils 13. 14 directly affects th ll'lagnitude f the terminal voltage of the machine. The M. M. F. due to the coils l2 and 14 also produces an E. M. F. in the winding 3 which I will refer to as back E. M. F. and which appears at the brushes 7, 8 and is of opposite direction to the E. M. F. generated and appearing at the brushes 5, 6, In this way said M. M. F. indirectly affects the magnitude of the terminal voltage by reducing the effective exciting E. M. F. It will thus be .seen that the effective magnetization of the machine will diminish very rapidly with increasing load and regardless of the nature of said load, because of the increase in the magnetization due to the coils 13, 14 and because of the consequent decrease in the magnetization due t the coils 9, 10, 11, 12. The amount by which the terminal voltage will vary with the varying speed mainly depends upon the number of turns of the coils 13 and 14. If the machine is connected to a storage battery then the magnetization'due to the coils 9, 10, 11, 12 will decrease still more rapidly with increasing speed and load because the back E. M. F.,generated at the brushes 7, 8 by rotation in the flux due to the coils 13, 14 will vary as before while the main E. M. F. appearing at the brushes 5, 6 will be kept practically constant by the storage battery connected thereto.

The foregoing description indicates that the objects aimed at are only partly achieved by the arrangement shown in Fig. 1, but the explanation of the mode of operation of that simple arrangement will make it easier and simpler to explain the mode of operation of the more'complete arrangement'showri in Fig. 2. The latter difl'ers from the former in that the poles N S forming the central portions of the two groups of mechanical poles N N N and S S S are also provided with main exciting coils '15, 16 included between the main and the auxiliary brushes. The coils 15 and 16 are so connected as to magnetize these middle poles in the manner indicated by the capital letters, thus producing a true 2-pole field, each electrical ,pole of which is divided up into three mechanical poles of like polarity. At no load the whole of the active ma-- tcrial is therefore fully utilized and the voltages generated in the commuted winding 4 are all added at the brushes 5 and 6. The voltage appearing at the brushes 7, 8 however only amounts to about of the total voltage generated in the winding 3. This is due to the fact that the auxiliary brushes are displaced,by 60 electrical de rees from the neutral axis of the 2-pole old. The connections aresuch that the auxiliary E. M. F. appearing at theauxiliaryhrushes at no load is added to the main EJM. F. appearing at the main brushes, the effective exciting'E. M. F. then being equal to the sum of the two E. M. F.s. When the load current flows through the reversing coils 13 and. 14 then the total magnetization of the poles S N is reduced because coils 13 and 14 are so connected as to oppose coils '15, 16 and the point is soonreached when the magnetization, of these middle poles becomes'zero, thus reestablishing the conditions obtaining in Fig. 1 at no load. As the load increases the middle poles are magnetized in an opposite direction and therefore change their polarity, S, becoming a north ole (1n) and N a. south pole (8,). When the middle poles are neutral the au'xiliary voltage appearing at the brushes 7, 8 and which at first assisted the main voltage appearing'at brushes 5,. 6, is zero and the effective exciting E. M F. equals the main E. M. F. When the middle poles reverse 1 that no-armature reaction flux can be prescase.

' portional to the current output.

cut as long as the three groups of poles clearly indicated in that figure are magnetically independent. It is, however, by. no means necessary that this should be the machines successfully even when all the mechanical poles are magnetically linked and it is often desirable to do so. A constructa'on with magnetically linked poles is also considerably more convenient in practice than the magnetically independent structure diagrammatically indicated in'Fig 1. The armature reaction flux is of course pro- It has no direct influence on the terminal voltage of the machine but it does affect the auxiliary I voltage at the brushes 7 8 in just the 'same Way as does the fiux due to the reversing coils. 13, 14. The armature reaction flux therefore also tends to reduce the effective exciting voltage of the machine but does not reduce it quite as rapidly as the reversing coils 13 and 14. It follows that the load characteristic of the machine will be of the same general character whether the reduction of the effective exciting E. M. F. is brought about by the reversin coils 13, 14 or by armature reaction but t ere will be a difference in de ree between the two load characteristics. his condition makes it possible for the designer to adjust the characteristic to the shape required by making use of the armature action only, 0 the reversing coils only, or of a combination of the two means.

- When all the mechanical poles have a common magnetic yoke it then becomes necessary to make provision for destroying or controlling the armature reaction due either to the working or the exciting armature currents. One way of controlling these armature reactions is shown in Fig. 3. It is because of the possibility of using magnetically independent, as well as magnetically dependent polar projections, that the Fig. 2 has been left indefinite as to the formation of the field structure.

In Figs. 1 and 2 the armatureis shown provided with two commuted windings. While such a construction is possible it is undesirable from a practical point of view and was only illustrated in order to simplify the descriptiou of the mode of operation of these machines.

It will readily be understod by those It is quite possible to operate such gle coil.

skilled in the art that the two commuted windings can be replaced by a single winding and that this construction would naturally be used in practice.

In Fig. 3 all the polar projections 28-29 -30 313233 are magnetically linked to each other by means of the yoke 27. The armature of Fig. 3 is wound for two poles and carries one commuted winding 4 only. The disposition of the main and auxiliary brushes is the same in the previous figures. The main exciting coils 9, 10 and are connected between the brushes 5 and 7, while the exciting coils 11, 12 and 16 are 1 connected between the brushes 6 and 8. The

armature reaction due to the exciting current circulating in the commuted winding 4 is taken care of by means of the coils 17, 18, 19, 20, 21 and 22 connected in series with the main exciting coils and producing a magnetization coaxial with the center line of the poles 28 and 31. It will be noticed that the coils 17 and 9 which are both located on the pole 28 are connected in series and produce oppositely directed magnetizations. It is clear that these two coils can be replaced by a single one, provided that this new coil is given a number of turns equal to the turns in 9 less the turns in 17. The coils 15, 19; 11, 20; and 16, 22 can be similarly combined, while the coils 18, 10; and 12, 21 produce magnetizations in the same direction and do not offer any material advantage if combined and replaced by a sin- The armature reaction due to the load current is coaxial to the brush line 5, 6 and is taken care of to any desired extent by the neutralizing series coils 23, 24, 25 and 26. The reversing series coils 14, 13 control the magnitude and the polarity of the magnetization of the poles and 33 in the same manner as in the previous figures. These middle or auxiliary poles 30 and 33 carry in addition coils 34 and 35 connected in parallel to the terminals or to the main brushes 5, 6 of the machine. 'The mag netization they produce is, therefore, proportional to the terminal voltage. They l may be connected so as to help or so as to oppose the magnetization produced by the main exciting coils 15, 16 placed on the said poles.

lVhen the dynamo is made use of for the I purpose of charging storage batteries then the coils 34 and 35 can be connected so as to oppose the main exciting coils 15, 16 and assist the coils 13, 14, in which case they will tend to reduce the current supplied by the dynamo to the battery as the battery voltage increases. Their effect will not be Very marked at low speeds, but it will be quite considerable at the higher speeds, and particularly when the polarity of the poles 30 and 33 has been reversed owing to the influence of the series coils 13, 14. This can be readily recognized from the fact that the coils 34, 35 magnetize in the same direction as the coils 13, 1 1. The latter tend to reduce the total magnetization of the machine and therefore the terminal voltage thereof. The former are connected to act in the same direction and must, therefore, produce the same result, their effect increasing with increasing terminal voltage.

Another way in which the shape of the load characteristic curve of the machine can be influenced is by the use of coils such as 36, 37, 38 and 39 connected in parallel to the main brushes 5, 6 and so disposed as to only influence that part of the flux threading the armature which does not affect the voltage at the auxiliary brushes 7, 8. To this end these coils are disposed on the poles 28, 29 31 and 32. If they are so connected as to magnetize in the same direction as the main exciting coils 9, 10, 11, 12 then they will have the tendency to prevent the characteristic curve from droppin rapidly with .increasing speed and load. The greater the proportion of the total initial magnetization of the poles 28, 29, 31 and 32 supplied by these auxiliary coils 36, 37, 38 and 39 the higher will be the characteristic curve at a given high speed. If these auxiliary coils oppose the main exciting coils then a more drooping characteristic will be obtained. In order to secure the exact characteristic required for a particular make of storage battery it may be necessary to make use of a combination of all the various means for adjusting the characteristic of the machine shown in Fig. 3 but the neutralizing coils 17, 18, 19, 20, 21 and 22 designed to take care of the armature reaction due to the exciting current can usuallv be dispensed with. In other cases some only of the adjusting means need be employed and it is often possible to omit the neutralizing windings 23, 24, 25 and 26.

Fig. 4 shows a somewhat different mechanical arrangement of the principal coils shown in Fig. The machines are however otherwise identical. The main exciting coils 10, 15, 11 and 9, 16, 12 of Fig. 3 have been replaced by single coils 40 and 41. respectively and each embracing three of the mechanical poles of the machine. Similarly the neutralizing coils 23, 24 and 25, 26 have been replaced by the single coils 42 and 43 each embracing two of the mechanical poles but producing identical magnetic effects as the corresponding coils of Fig. 3. The reversing coils 13, 14, the adjusting coils 31', 35 and 36,37 38, 39 are identical with those of Fig. 3. The connections in Fig. 4 are it the same as those of Fig. 3.

While I have described my invention as applied to generators with two-poh armatures, yet it will be readily understood that the invention is in no way restricted to disposed in s While it will be mostly convenient to dispose the neutralizing windings 23, 24, 25, 26

in :the manner shovyn in Figs. 3 or 4, yet these windi'n will be quite as efieetive if ots provided in the vicinity of the pole faces and in a manner now well understood.

Having fully described my invention, What I claim as new and desire tosecure by Letters Patent of the United States, is:

1. In a dynamo electric machine, the combination with a revolving member having an n-pole winding, main brushes and an auxiliary brush displaced by about 120/n degrees from a main brush, of a stationary member carrying coils adapted to produce a 3n pole field, certain of said coils being connected in series between a main and an auxiliary brush.

2.' In a dynamo electric machine, the combination with a stationary member having 3% mechanical poles each provided with a coil, of a revolving member having an npole winding, m in brushes and an auxiliary brush displaced by sixty electrical degrees from one of the main brushes, and means connecting certain of the coils .on the stationary member in series with a main and an auxiliary brush.

3. In a dynamo electric machine, the combination with a stationary member having 3n mechanical poles Q/n ofwhich are each provided with a coil, of a revolving member having an n-pole winding, main brushes and an auxiliary brush displaced by about 120/4 degnees from one of the main brushes, and means connecting certain of the coils on the stationary member in series with a main and an auxiliary brush. 1

4. In a dynamo electric machine, the combination with a stationary member having 3% mechanical poles 2n of which are each rovided with a coil, of a revolving member having an 'n-pole winding, main brushes and an auxiliary brush displaced by about 120/? degrees from one of the main brushes, means connecting vcertain of the field coils in series with a main and an auxiliary brush, and means for producing an auxiliary magneto motive forceon certain of the mechanical poles. v

5. In a dynamo electric machine, the combination with a stationary member having 3n mechanical poles, of a revolving member having an 'n-pole winding, main brushes and auxiliary brushes displaced sixty electrical degrees from the main brushes. each brush being located between adjacent mechanical poles, main exciting coils on the poles adjacent to the main brushes and connected in series betweema main and an auxiliary brush.

6. [In a dynamo electric machine, the combination with a stationary member having 3% mechanical poles, of -a revolving member having an n-pole winding, main brushes and auxiliary brushes displaced sixty degrees from the main brushes, each brush being located between adjacent mechanical poles, main exciting coils on the poles adj acent to the inain brushes and connected in series between a main and an auxiliary brush, and auxiliary coils on the remaining mechanical poles.

7. In a dynamo eleotricmachine, the combination with a stationary member having electrical 3n mechanical poles, of a revolving member having an n-pole winding, main brushes and auxiliary brushes displaced sixty electrical degrees from the main brushes, each brush being located between adjacent mechanical poles, main exciting coils on each mechani- .-cal pole, said coils being connected in series between a main and an auxiliary brush. and auxiliary coils located on poles displaced ninety electrical degrees from the main bruslhes.

8. In adynamo electric machine, the combi-nation with a stationary member having 3n mechanical poles, of a revolving member having an n-pole winding, main brushes and auxiliary brushes displaced sixty electrical degrees from the main brushes, each brush being located between. adjacent mechanical poles, main exciting coils on each of the mechanical poles, said coils being cbnnected in series between a main and an auxiliary brush.

9. In a dynamo electric machine, a stationary member having windings adapted to produce an 'n-pole field, a revolving member having an n-pole winding, and means dependent upcri the load current for changing the stator field from an n-pole field to a 3n pole field and vice versa.

10. In a dynamo electric machine, a stationary member having windings adapted to produce an n-pole field, a revolving inem-' her having an n-p-ole winding and means for producing an additional magneto motive force which will operate to change the iataitfr field from an n-pole field to a 3n pole 11. In a dynamo electric machine, a stationary member having 3n mechanical poles and windings adapted to produce an n-pole field distributed over all the mechanical poles, a revolving member having an 'n-pole windingfmeans dependent upon the load current for changing the stator field from an n-pole field to a 3n pole field and vice versa.

12. In a dynamo electric machine, a mtionary member having 3n mechanical poles and windings adapted to'produce an n-pole field distributed over v all the mechanical poles, a revolving member having an n-pole winding, means for producing an additional magneto motive force for changing the stalor field from an npole field to a 3n pole field.

13. In a dynamo electric machine, the combination with a stationary member having 3n mechanical poles, of a revolving member having an n-pole winding, main brushes and auxiliary brushes displaced sixty electrical degrees from the main brushes,,each brush being located between adjacent mechanical poles, main exciting coils on the poles adjacent to the main brushes and connected in series between a main and an auxiliary brush, and adjusting coils on the same poles as the main exciting coils, said adjusting coils being connected in parallel with the main brushes.

14. In a dynamo electric machine, the combination with a stationary member having 31?, mechanical poles, of a revolving member having an a-polc winding, main brushes and auxiliary brushes displaced sixty electrical degrees from the main brushes, each brush being located between adjacent mechanical poles, main exciting coils on the poles adjacent to the main brushes and connected in series between a main and an auxiliary brush, and neutralizing coils on the same poles as the main excitin coils.

15. n a dynamo electric machine, the combination with a stationary member having 3n mechanical poles, of a revolving member having an n-pole Winding, main brushes and auxiliary brushes displaced sixty electrical degrees from the main brushes, each brush being located between adjacent mechanical poles, main exciting coils on the poles adjacent to the main brushes and connected in series between a main and an auxiliary brush, and adjusting coils on the remaining mechanical poles,

said coils being connected in parallel to the main brushes.

16. In a dynamo electric machine, the combination with a stationarymember having 3n mechanical poles, of a revolving member having an n-pole winding, main brushes and auxi "v brushes displaced sixty electrical dc .aes from the main brushes, each brush being located between adjacent mechan cal poles, main exciting coils on the les adjacent to the main rushes and connected in series between a main and an auxiliary brush, and auxiliary coils on the remaining mechanical poles connected to carry at least part of the load current.

17. In a dynamo electric machine, the combination with a stationary member having 3% mechanical poles each provided With a coil, of a revolvin member havin an n-pole winding, main rashes and auxiliary brushes displaced by sixty electrical degrees from the main brushes, and means connecting certain of the coils on the Stationary member in series with a. main and an auxiliary brush.

18. In a dynamo electric machine, the combination with a stationary member haw ing 3n mechanical poles cach provided with a coil, of a revolving member having an mpolc winding, main brushes and an auxil iary brush, each of said brushes being located between adjacent poles, and means connecting certain of the coils on the stationary member in series with a main and an auxiliary brush.

19. In a dynamo electric machine. the combination with a stationary member having 3n mechanical poles and windings on certain of said poles, of a revolving member having main brushes and an auxiliary brush each brush being located in an intcnpolar space, and an exciting circuit comprising the auxiliary brush, a main brush, and windings on poles adjacent to a main brush.

20. In a dynamo electric nnu'hine, the combination with a stationary member hav ing mechanical poles and windings on certain of said poles, of a revolving member having main brushes and an auxiliary brush, and an exciting circuit comprising the auxiliary brush, a main brush and windings on poles adjacent to a main brush, and a working circuit comprising the main brushes and a winding on the stationary member, said winding being displaced by electrical degrces from said main brushes.

21. In a dynamo electric machine, the ombination with a stationary member having 3n mechanical poles and exciting Windings on certain of said poles, of a revolving member having main brushes and an auxiliary brush each located in an inter-polar space. an exciting circuit comprising the auxiliary brush, a main brush, and the can citing windings on poles adjacent to a main brush, and means for neutralizing the armature reaction along the axis of the main brushes.

In a dynamo electric machine, the combination with a field structure comprising 3n equally spaced mechanical poles and windings thereon, of an armature having an n-pole winding, main brushes and an auxiliary brush, each brush being located be tween adjacent mechanical poles, and an exciting circuit comprising the main brushes. an auxiliary brush and windings on poles adjacent to a main brush, and a working circuit comprising the main brushes and a winding displa ed approximately ninety electrical degrees from said main brushes.

In a dynamo electric machine, the combination with a stationary member having 3n mechanical poles and exciting wind-- ings adapted to produce an n-pole held dis tributed over all the mechanical poies of a revolving member having an n-pole Windi g, main and auxiliary brushes, an exciting circuit comprising a main and an auxiliary brush and certain of the exciting windings, and means for producin a magneto motive force for changing t e stator field from an n-pole field to a 3n ole field.

24. In a dynamo electric mac ine, the combination with a stationary member having 3n mechanical poles and exciting windings adapted to produce an n-pole field dis tributed over all the mechanical poles, of a revolving member having an n-pole winding, main and auxiliary brushes, an exciting circuit comprising a main and an auxiliary brush and certain of the exciting windings, means for producing a magneto motive force for changing the stator field from an n-pole field to a 3n pole field, and means for neutralizing the armature reaction along the axis of the main brushes.

25. In a dynamo electric 'machine, the

combination with a stationary member having 31!, mechanical poles and exciting windings adapted to produce an n-pole field distributed over all the mechanical poles, of a revolving member having an n-pole winding, main and auxiliary brushes, each brush being located between mechanical poles, an exciting circuit comprising a main and an auxiliary brush and certain of the exciting windings, means for producing a magneto motive force for changing the stator field from an n-pole field to a 3n pole field, and adjusting windings on the poles adjacent to the main brushes and connected in parallel with said brushes.

In testimony whereof, I have hereunto set my hand and aflixed my seal in the presence of the two subscribing witnesses.

VALERE ALFRED FYNN. a 5.]

Witnesses:

ELIZABETH BAILEY, W. A. ALEXANDER.

M coplel of this patent may be obtained for tlve cents each, by addressing the Commissioner 0: Patents. Washington, D. e." 

